1. Field of the Invention
The present invention relates to a drive shaft bearing structure for boat.
2. Description of Background Art
Conventional drive shaft bearing structures for boats are known. One example is shown in FIG. 8 (Japanese Patent Laid-open No. Hei 7-112697).
FIG. 8 of this document shows a drive shaft 1, a driven-side coupler 2 connected to a driving-side coupler of an engine (not shown) fixed to the front end of the drive shaft 1, and an impeller (not shown) fixed to the rear end of the drive shaft 1. Power from the engine is transmitted to the impeller, whereby the impeller is rotationally driven.
The bearing structure includes a bearing body 4 for rotatably supporting the drive shaft 1 relative to a boat body 3.
The bearing body 4 includes a bearing member 5 for rotatably (in this case, rotatably through the bearing body 4) supporting the drive shaft 1 relative to the boat body 3. The bearing member 5 includes an inner lace 5a making contact with an outside circumferential surface of the drive shaft 1 (in the structure shown, an outside circumferential surface of a sleeve 1xe2x80x2 rotated as one body with the shaft 1), and an outer lace 5c disposed on the outside of the inner lace 5a with a rotary body 5b therebteween.
In such a bearing structure, in order that the drive shaft 1 (in the structure shown, the sleeve 1xe2x80x2, here and hereinafter) can be inserted into and drawn out of the bearing member 5, the outside diameter of the drive shaft 1 is set to be slightly smaller than the inside diameter of the inner lace 5a. Generally, however, the structure is so constituted that the drive shaft 1 and the inner lace 5a are rotated together.
However, with the structure described above, a reaction force from the impeller acts on the drive shaft 1. This reaction force acts in a complicated combination of thrust forces, twisting forces and bending forces. In addition, in considering how the structure is assembled, the clearance between the drive shaft and the inner lace cannot be reduced. Therefore, there are often is the case where the drive shaft 1 and the inner lace 5a are not rotated together, and the outside circumferential surface 1a of the drive shaft 1 and the inside circumferential surface of the inner lace 5a make sliding contact with each other. This results in the outside circumferential surface 1a of the drive shaft 1 and/or the inside circumferential surface of the inner lace 5a being gradually worn.
One of the objects of the present invention to solve the above problems, and to provide a drive shaft bearing structure for boat in which wearing of the inside circumferential surface of the drive shaft and/or the inside circumferential surface of the inner lace can be reduced or prevented.
In order to attain the above object, the structure of the present invention includes a bearing member for rotatably supporting a drive shaft for driving an impeller on a boat body, the bearing member comprising an inner lace making contact with an outside circumferential surface of the drive shaft, and an outer lace disposed on the outside of the inner lace with a rotary body therebtween. Also included is a connecting member for rotating both the drive shaft and the inner lace provided between the outside circumferential surface of the drive shaft and the inner lace.
In second aspect of the present invention, the connecting member of the structure is a ring-shaped elastic body pressed against the outside circumferential surface of the drive shaft and a side surface of the inner lace. Further, a plurality of the bearing members are provided at a spacing or spacings, and the connecting member is disposed between the bearing members.
In addition, in another aspect of the present invention, the connecting member is a ring-shaped elastic body which is disposed in a ring-shaped groove formed in a portion facing to the inner lace of the outside circumferential surface of the drive shaft and which is pressed by the inner lace.
As described above, the drive shaft bearing structure includes a bearing member for rotatably supporting a drive shaft for driving an impeller on a boat body, the bearing member comprising an inner lace making contact with an outside circumferential surface of the drive shaft, and an outer lace disposed on the outside of the inner lace with a rotary body therebetween. Further, a connecting member for rotating both the drive shaft and the inner lace is provided between the outside circumferential surface of the drive shaft and the inner lace. According to this structure, even when a reaction force from the impeller acts on the drive shaft and the reaction force acts as the result of a complicated combination of thrust forces, twisting forces and bending forces, the drive shaft and the inner lace are rotated together by the connecting member.
Therefore, sliding contact between the outside circumferential surface of the drive shaft and the inside circumferential surface of the inner lace is prevented, and premature wearing of the outside circumferential surface of the drive shaft and/or the inside circumferential surface of the inner lace is prevented.
Further, the connecting member is made of a ring-shaped elastic body pressed against the outside circumferential surface of the drive shaft and a side surface of the inner lace. Therefore, it is possible to provide the connecting member without altering the drive shaft and/or the inner lace.
In addition, a plurality of the bearing members are provided at a spacing or spacings. Therefore, the drive shaft can be supported securely and in a stable condition by the plurality of the bearing members. Since the connecting member is disposed between the bearing members, the outside circumferential surface of the drive shaft and a side surface of the inner lace of the bearing member disposed adjacently are favorably pressed against each other by the connecting member. Therefore, sliding contact between the outside circumferential surface of the drive shaft and the inside circumferential surface of the inner lace is prevented more securely, and wearing of the outside circumferential surface of the drive shaft and/or the inside circumferential surface of the inner lace is prevented more securely.
The connecting member can also be a ring-shaped elastic body disposed in a ring-shaped groove formed in a portion facing to the inner lace of the outside circumferential surface of the drive shaft and pressed by the inner lace. In this configuration, the outside circumferential surface of the drive shaft and the inside circumferential surface of the inner lace are also connected directly, and sliding contact between both of the surfaces can be prevented. Therefore, wearing of the outside circumferential surface of the drive shaft and/or the inside circumferential surface of the inner lace is again prevented in a secure manner.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.